This invention relates generally to parenteral fluid administration (referred to herein as "intravenous administration" or "IV administration") and, more particularly, to an improved IV drop sensing unit and dedicated or associated drip chamber for use in an IV fluid administration system whereby installation, retention and removal are enhanced and aid is afforded in preventing use of chambers with operating characteristics differing from those desired.
IV fluid administration has conventionally involved use of a disposable fluid administration set with an elongated drip chamber. Discrete fluid drops fall from a drop former to a reservoir and may be observed or detected through a transparent wall as they fall through the chamber.
Instrumentation systems for monitoring or controlling the rate of gravity flow through such administration sets, or actually pumping fluid under positive pressure through them, have made use of drop sensing units. One such unit, described in U.S. Pat No. 3,596,515, removably clamps onto the drip chambers of a variety of sizes and shapes, and utilizes a self-contained light source and photoelectric sensor to detect drops.
Proper positioning of the sensing unit on the chamber of these prior systems so that the light beam of the sensor intercepts all falling drops is a requirement. Various expedients to aid in proper positioning have been used.
With certain types of fluid administration systems, it is especially important that only sets with certain predetermined operating characteristics be utilized. One such system provides for directly setting the desired delivery rate in milliliters per hour and, in turn, monitors the drop rate via the sensing unit and compares it with the desired rate. As is apparent, it is assumed with such a system that the drops are of a specified size, e.g., 60 drops per milliliter. Should the drop size differ, e.g., the drops be 20 drops per milliliter in size, performance clearly is adversely affected.
For accuracy consideration, it is particularly desirable with volumetric systems of the type just described that there be minimal variation in drop size from set to set. This is a matter that is subject to control in a given manufacturing operation tailored to accomplish that result.
Some prior art systems have employed sensing units with mounting elements that engage mating retention elements on a dedicated or associated set. This is for the purpose of positioning and preventing use of other than the associated set. However, these prior systems have not been entirely effective in establishing and maintaining proper positioning. Moreover, such sensing units have been inconvenient to install and remove from the drip chamber of the dedicated or associated set.
It will be appreciated from the foregoing that there has been and is a continuing need for an improved drop sensing unit and associated, dedicated drip chamber with cooperating means to aid in easily, rapidly, and reliably positioning the unit and chamber relative to one another. The sensing unit should desirably aid in preventing use on any drip chamber other than the specially designed and manufactured item. A further attribute desired is that the sensing unit be adapted for each installation and removal.